Power amplifier module

ABSTRACT

A power amplifier module includes a combining circuit including a combiner. The combining circuit further includes a first inductor connected in series between an output terminal of a first amplifier and the combiner, a second inductor connected in series between an output terminal of a second amplifier and the combiner, and a second capacitor having an end connected to the combiner and another end grounded. A phase of a third signal from the output terminal of the first amplifier to the second amplifier through the combiner is delayed by about 45 degrees in the first inductor and the second capacitor, and is delayed by about 45 degrees in the second inductor and the second capacitor. A phase of the third signal from the output terminal of the first amplifier to the second amplifier through the first capacitor is advanced by about 90 degrees.

BACKGROUND

Priority is claimed from Japanese Patent Application No. 2017-006036filed on Jan. 17, 2017. The content of this application is incorporatedherein by reference in its entirety.

The present disclosure relates to a power amplifier module. A mobilecommunication device such as a cellular phone is provided with a poweramplifier for amplifying a transmit signal. For example, JapaneseUnexamined Patent Application Publication No. 2012-54874 discloses aradio-frequency amplifier including, to meet requirements for highoutput power, a power divider circuit that divides an input signal intosignals, a set of amplifier elements that amplify the respective signalsthat are divided, and a power combining circuit that combines theamplified signals. The radio-frequency amplifier includes an isolationresistor that electrically connects output terminals of the set ofamplifier elements to each other, and a passive element connected inparallel to the isolation resistor to increase impedance. Thus, if asignal from one path enters the other path in an unbalanced mode, theisolation resistor absorbs power, which ensures isolation between theamplifier elements.

There is a demand for improved performance of power amplifiers inaccordance with a change in the communication standard to be applied. Incommunication standards such as Long Term Evolution-Advanced(LTE-Advanced), carrier aggregation that enables simultaneoustransmission of a plurality of transmit signals of different frequencybands is used. Power amplifiers with improved output power and improvedoutput linearity are demanded accordingly.

Typically, the performance of an amplifier element is maximized when theimpedance on the load side as seen from the amplifier element isapproximately a real number. In this regard, in the configurationdisclosed in Japanese Unexamined Patent Application Publication No.2012-54874, a single passive element performs impedance matching betweenthe amplifier elements and the load side of the radio-frequencyamplifier, which results in a substantially maximum imaginary part ofthe impedance of the amplifier elements on the load side. Accordingly,depending on the configuration disclosed in Japanese Unexamined PatentApplication Publication No. 2012-54874, there is a limitation onimprovements of the performance of the amplifier elements, and it isdifficult to improve linearity.

BRIEF SUMMARY

Accordingly, the present disclosure provides a power amplifier modulethat achieves high output power and high linearity.

According to embodiments of the present disclosure, a power amplifiermodule includes a divider circuit that divides an input signal into afirst signal and a second signal, a first amplifier that amplifies thefirst signal and outputs a third signal, a second amplifier thatamplifies the second signal and outputs a fourth signal, a combiningcircuit including a combiner that combines the third signal and thefourth signal and that outputs an amplified signal of the input signal,a resistance element that electrically connects an output terminal ofthe first amplifier and an output terminal of the second amplifier toeach other, and a first capacitor connected in parallel to theresistance element. The combining circuit includes a first inductorconnected in series between the output terminal of the first amplifierand the combiner, a second inductor connected in series between theoutput terminal of the second amplifier and the combiner, and a secondcapacitor having an end connected to the combiner and another endgrounded. A phase of the third signal from the output terminal of thefirst amplifier to the output terminal of the second amplifier throughthe combiner is delayed by about 45 degrees in a first phase shifterincluding the first inductor and the second capacitor, and is delayed byabout 45 degrees in a second phase shifter including the second inductorand the second capacitor. A phase of the third signal from the outputterminal of the first amplifier to the output terminal of the secondamplifier through the first capacitor is advanced by about 90 degrees.

According to embodiments of the present disclosure, it may be possibleto provide a power amplifier module that achieves high output power andhigh linearity.

Other features, elements, and characteristics of the present disclosurewill become more apparent from the following detailed description ofembodiments of the present disclosure with reference to the attacheddrawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example configuration of a poweramplifier module according to a first embodiment of the presentdisclosure;

FIG. 2 is an equivalent circuit diagram of a combining circuit in acomparative example in an unbalanced mode;

FIG. 3 is an equivalent circuit diagram of the combining circuit in thecomparative example in a balanced mode;

FIG. 4 is a diagram illustrating the locus of impedance of the combiningcircuit in the comparative example in the balanced mode;

FIG. 5 is an equivalent circuit diagram of a combining circuit of thepower amplifier module according to the first embodiment of the presentdisclosure in the unbalanced mode;

FIG. 6 is an equivalent circuit diagram of the combining circuit of thepower amplifier module according to the first embodiment of the presentdisclosure in the balanced mode;

FIG. 7 is a diagram illustrating the locus of impedance of the combiningcircuit of the power amplifier module according to the first embodimentof the present disclosure in the balanced mode;

FIG. 8 is a diagram used to describe impedance transformation in a phaseshifter;

FIG. 9 is a diagram illustrating another example configuration of thepower amplifier module according to the first embodiment of the presentdisclosure;

FIG. 10 is a diagram illustrating another example configuration of thepower amplifier module according to the first embodiment of the presentdisclosure;

FIG. 11 is a diagram illustrating an example configuration of a poweramplifier module according to a second embodiment of the presentdisclosure;

FIG. 12 is a diagram illustrating another example configuration of thepower amplifier module according to the second embodiment of the presentdisclosure;

FIG. 13 is a diagram illustrating an example of the mounting of thepower amplifier module according to the first embodiment of the presentdisclosure; and

FIG. 14 is a diagram illustrating an example of the mounting of thepower amplifier module according to the second embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described in detailhereinafter with reference to the drawings. The same or substantiallythe same elements are identified with the same numerals and are notdescribed repeatedly.

FIG. 1 is a diagram illustrating an example configuration of a poweramplifier module according to a first embodiment of the presentdisclosure. A power amplifier module 100 illustrated in FIG. 1 isincorporated in a cellular phone, for example, and is used to amplifythe power of signals to be transmitted to a base station. The poweramplifier module 100 amplifies the power of signals based oncommunication standards such as second generation mobile communicationsystems (2G), third generation mobile communication systems (3G), fourthgeneration mobile communication systems (4G), fifth generation mobilecommunication systems (5G), Long Term Evolution-Frequency DivisionDuplex (LTE-FDD), Long Term Evolution-Time Division Duplex (LTE-TDD),LTE-Advanced, and LTE-Advanced Pro. The communication standards ofsignals to be amplified by the power amplifier module 100 are notlimited to those described above.

The power amplifier module 100 includes a divider circuit 110,transistors Q1 a and Q1 b, a combining circuit 120, resistance elementsR1 a, R1 b, and R2, and a capacitor C2. The divider circuit 110, thetransistors Q1 a and Q1 b, and the combining circuit 120 form aclosed-loop circuit. The constituent elements will be described indetail hereinbelow.

In the divider circuit 110, a distributor 112 approximately equallydivides a radio-frequency (RF) signal RFin (input signal) input from aninput terminal into a signal (first signal) on the transistor Q1 a sideand a signal (second signal) on the transistor Q1 b side. The RF signalRFin has a frequency of about several gigahertz (GHz), for example. Thedivider circuit 110 includes capacitors C1 a and C1 b. The capacitors C1a and C1 b have first ends connected to the distributor 112 and secondends connected to bases of the transistors Q1 a and Q1 b, respectively.The capacitors C1 a and C1 b remove the direct-current component of theRF signal RFin. The configuration of the divider circuit 110 is notlimited to that described above. For example, the divider circuit 110may be constituted by a 3-dB coupler or a lumped circuit.

Each of the transistor Q1 a (first amplifier) and the transistor Q1 b(second amplifier) is an amplifier that amplifies a signal output fromthe divider circuit 110. While the amplifier is not limited to anyspecific type, a heterojunction bipolar transistor (HBT) is used as eachof the amplifiers, by way of example, in FIG. 1. Specifically, thetransistor Q1 a has a base connected to the second end of the capacitorC1 a, an emitter grounded, and a collector (output terminal) from whichan amplified signal (third signal) obtained by amplifying the RF signalis output. Likewise, the transistor Q1 b has a base connected to thesecond end of the capacitor C1 b, an emitter grounded, and a collector(output terminal) from which an amplified signal (fourth signal)obtained by amplifying the RF signal is output. A bias voltage or biascurrent Bias is supplied to the base of the transistor Q1 a via theresistance element R1 a, and the bias voltage or bias current Bias issupplied to the base of the transistor Q1 b via the resistance elementR1 b. Each amplifier may be any other transistor such as a field-effecttransistor (metal-oxide-semiconductor field effect transistor (MOSFET)).When a MOSFET is used instead of a bipolar transistor, a collector, abase, and an emitter may be read as a drain, a gate, and a source,respectively.

The combining circuit 120 includes an inductor L1 a (first inductor), aninductor L1 b (second inductor), a capacitor C3 (second capacitor), anda combiner 122. The combiner 122 combines the amplified signal (thirdsignal) output from the collector of the transistor Q1 a and theamplified signal (fourth signal) output from the collector of thetransistor Q1 b and outputs an amplified signal RFout1. The inductor L1a is connected in series between the collector of the transistor Q1 aand the combiner 122, and the inductor L1 b is connected in seriesbetween the collector of the transistor Q1 b and the combiner 122. Thecapacitor C3 has an end connected to the combiner 122 and another endgrounded. The capacitor C3 has a capacitance that is about twice thecapacitance of the capacitor C2, for example. The functions of theinductors L1 a and L1 b and the capacitor C3 will be described below.

The resistance element R2 electrically connects the collector of thetransistor Q1 a and the collector of the transistor Q1 b to each other.

The capacitor C2 (first capacitor) is connected in parallel to theresistance element R2. Specifically, the capacitor C2 has an endconnected to the collector of the transistor Q1 a and another endconnected to the collector of the transistor Q1 b.

Next, the operations of the power amplifier module 100 in an unbalancedmode and a balanced mode will be described with reference to FIGS. 2 to8. The balanced mode is a mode in which both the power level and phaseof the amplified signal output from the transistor Q1 a havesubstantially the same values as the power level and phase of theamplified signal output from the transistor Q1 b, and the unbalancedmode is a mode in which at least one of the power level and phase of theamplified signal output from the transistor Q1 a has a different valuefrom the at least one of the power level and phase of the amplifiedsignal output from the transistor Q1 b. The unbalanced mode occurs dueto variations in the production of transistors or transmission lines,for example.

FIG. 2 is an equivalent circuit diagram of a combining circuit in acomparative example in the unbalanced mode. In this specification, in acomparative example (comparative example 10), a configuration (acombining circuit 12) is used that does not include the capacitor C3included in the combining circuit 120 illustrated in FIG. 1 but includestransmission lines Lx and Ly instead of the inductors L1 a and L1 b,respectively. The transmission lines Lx and Ly are X/8 lines, where Xdenotes the wave length of the RF signal, and the RF signal has phaseshifts of 45 degrees across the transmission lines Lx and Ly. Forconvenience of illustration, the constituent elements included in thecomparative example 10 are identified with numerals similar to those ofthe corresponding constituent elements of the power amplifier module100.

Consideration is given to the case where, in the comparative example 10,an amplified signal output from one transistor enters the path on theother transistor side. Here, by way of example, a description will begiven of the case in which an amplified signal RFa output from thetransistor Q1 a enters the path on the transistor Q1 b side, whereas nodescription will be given of the case in which an amplified signal RFboutput from the transistor Q1 b enters the path on the transistor Q1 aside. The phase of the amplified signal RFa that passes through a node Aillustrated in FIG. 2 is delayed by about 45 degrees by passing throughthe transmission line Lx, and is further delayed by about 45 degrees bypassing through the transmission line Ly after passing through thecombiner 122 (see FIG. 2). Accordingly, the phase of the signal from thenode A to a node B through the transmission line Lx, the combiner 122,and the transmission line Ly is delayed by about 90 degrees with respectto the phase of the amplified signal RFa at the node A. In contrast, thephase of the signal from the node A to the node B through the capacitorC2 is advanced by about 90 degrees with respect to the phase of theamplified signal RFa at the node A. Therefore, in the unbalanced mode,the phase of the signal at the node B is approximately opposite to thephase of the signal at the node A. That is, even if an amplified signalin one amplification path enters the other amplification path, thesignal has amplitudes that cancel each other out, and isolation isensured between the amplifiers.

FIG. 3 is an equivalent circuit diagram of the combining circuit in thecomparative example in the balanced mode. In the balanced mode, an inputsignal is divided into signals having the same amplitude and the samephase by a divider circuit, and thus signals at both ends of theresistance element R2 and the capacitor C2 have the same amplitude andthe same phase. In the equivalent circuit illustrated in FIG. 3, theresistance element R2 and the capacitor C2 are not illustrated.

As illustrated in FIG. 3, the impedance on the combining circuit side asseen from the output of the transistors is represented by Z_(Q), thecharacteristic impedance of the transmission lines Lx and Ly isrepresented by Z₀, and the impedance on the load side as seen from thecombiner 122 is represented by Z_(L). Since the transmission line Lx andthe transmission line Ly are connected in parallel, the impedances onthe load side as seen from the output of the transmission lines Lx andLy are each equal to 2Z_(L).

FIG. 4 is a diagram illustrating the locus of impedance of the combiningcircuit in the comparative example in the balanced mode. In FIG. 4, thelocus of impedance when moving from the center (2Z_(L)) through thetransmission line Lx or the transmission line Ly is plotted on a Smithchart. In the comparative example, only one passive element (here, thetransmission line Lx or the transmission line Ly) performs phasetransformation and impedance transformation. Accordingly, the impedanceZ_(Q) on the combining circuit side as seen from the output of thetransistors moves away from the real axis and becomes an imaginarynumber (see FIG. 4). Typically, the performance of a transistor ismaximized when the impedance Z_(Q) on the combining circuit side as seenfrom the output of the transistor is approximately a real number. Inthis respect, in the configuration in the comparative example 10, asubstantially maximum imaginary part of the impedance Z_(Q) occurs,which imposes a limitation on improvements of the linearity of thetransistors.

FIG. 5 is an equivalent circuit diagram of a combining circuit of thepower amplifier module according to the first embodiment of the presentdisclosure in the unbalanced mode. The combining circuit 120 can beequivalently represented as a configuration (a combining circuit 120′)including a phase shifter 124 a (first phase shifter) constituted by theinductor L1 a connected in series with the signal path and a capacitorC3 a shunt-connected to the signal path, and a phase shifter 124 b(second phase shifter) constituted by the inductor L1 b connected inseries with the signal path and a capacitor C3 b shunt-connected to thesignal path (see FIG. 5). That is, each of the phase shifters 124 a and124 b has a configuration similar to that of an L-type low pass filter(LPF). In addition, as described below, the constants of the respectiveelements in the phase shifters 124 a and 124 b are designed such thatthe phase of an output signal is delayed by about 45 degrees withrespect to the phase of an input signal. In contrast, as in thecomparative example 10 illustrated in FIG. 2, the phase of the signalfrom the node A to the node B through the capacitor C2 is advanced byabout 90 degrees with respect to the phase of the amplified signal RFaat the node A. Therefore, the phase of the signal from the node A to thenode B through the phase shifter 124 a, the combiner 122, and the phaseshifter 124 b is approximately opposite to the phase of the signal fromthe node A to the node B through the capacitor C2. That is, even if anamplified signal in one amplification path enters the otheramplification path, the signal has amplitudes that cancel each otherout, and isolation is ensured between the amplifiers.

FIG. 6 is an equivalent circuit diagram of the combining circuit of thepower amplifier module according to the first embodiment of the presentdisclosure in the balanced mode. In the balanced mode, as in FIG. 3, theresistance element R2 and the capacitor C2 are not illustrated.

The phase shifter 124 a delays the phase of the signal by about 45degrees and performs impedance transformation between the impedance 2Z₁,on the load side as seen from the output of the phase shifter 124 a andthe impedance Z_(Q) on the load side as seen from the output of thetransistor Q1 a (not illustrated). Likewise, the phase shifter 124 bdelays the phase of the signal by about 45 degrees and performsimpedance transformation between the impedance 2Z₁, on the load side asseen from the output of the phase shifter 124 b and the impedance Z_(Q)on the load side as seen from the output of the transistor Q1 b (notillustrated).

FIG. 7 is a diagram illustrating the locus of impedance of the combiningcircuit of the power amplifier module according to the first embodimentof the present disclosure in the balanced mode. In FIG. 7, the locus ofimpedance when moving from the center (2Z_(L)) through the phase shifter124 a or the phase shifter 124 b is plotted on a Smith chart. In thepower amplifier module 100, two passive elements (the inductor L1 a andthe capacitor C3 a or the inductor L1 b and the capacitor C3 b) performphase transformation and impedance transformation. In the poweramplifier module 100, therefore, the impedance Z_(Q) on the combiningcircuit side as seen from the output of the transistors can be madeclose to the real axis (see FIG. 7).

FIG. 8 is a diagram used to describe impedance transformation in thephase shifter 124 a. As illustrated in FIG. 6, the phase shifter 124 aincludes the inductor L1 a connected in series with the signal path, andthe capacitor C3 a shunt-connected to the signal path. In addition, aninput voltage is represented by V₁, an output voltage is represented byV₂, an input current is represented by I₁, an output current isrepresented by I₂, the impedance on the phase shifter side as seen fromthe input terminal is represented by Z₁, the impedance on the phaseshifter side as seen from the output terminal is represented by Z₂, theinductance of the inductor L1 a is represented by L, the capacitance ofthe capacitor C3 a is represented by C, and the angular frequency of asignal relative to the center frequency is represented by ω.

The fundamental matrix of the phase shifter 124 a is represented byequation (1) below.

$\begin{matrix}{\begin{pmatrix}V_{1} \\I_{1}\end{pmatrix} = {\begin{pmatrix}{1 - {\omega^{2}{LC}}} & {j\; \omega \; L} \\{j\; \omega \; C} & 1\end{pmatrix}\begin{pmatrix}V_{2} \\{- I_{2}}\end{pmatrix}}} & (1)\end{matrix}$

Accordingly, a gain characteristic of the phase shifter 124 a satisfiesequation (2) below.

$\begin{matrix}{\frac{V_{2}}{V_{1}} = {\left( {\left( {1 - {\omega^{2}{LC}}} \right) - {\frac{1}{Z_{2}}j\; \omega \; L}} \right)^{- 1} = \frac{\left( {1 - {\omega^{2}{LC}}} \right) + {j\frac{\omega \; L}{Z_{2}}}}{\left( {1 - {\omega^{2}{LC}}} \right)^{2} + \left( {- \frac{\omega \; L}{Z_{2}}} \right)^{2}}}} & (2)\end{matrix}$

Furthermore, a gain characteristic of the phase shifter 124 a satisfiesequation (3) below.

$\begin{matrix}{\frac{V_{2}}{V_{1}} = {\left( {Z_{1}\left( {{j\; \omega \; C} - \frac{1}{Z_{2}}} \right)} \right)^{- 1} = {\frac{1}{Z_{1}}\frac{{- \frac{1}{Z_{2}}} - {j\; \omega \; C}}{\left( {- \frac{1}{Z_{2}}} \right)^{2} + \left( {\omega \; C} \right)^{2}}}}} & (3)\end{matrix}$

If the phase shifter 124 a has a phase difference of π/4, equation (4)below holds from equation (2) above.

$\begin{matrix}{{\tan^{- 1}\left( \frac{\; \frac{\omega \; L}{Z_{2}}}{\left( {1 - {\omega^{2}{LC}}} \right)} \right)} = \frac{\pi}{4}} & (4)\end{matrix}$

Likewise, equation (5) below holds from equation (3) above.

$\begin{matrix}{{\tan^{- 1}\left( \frac{\omega \; C}{\frac{1}{Z_{2}}} \right)} = \frac{\pi}{4}} & (5)\end{matrix}$

In addition, equation (6) below holds from equations (4) and (5) above.

$\begin{matrix}{\frac{\omega \; L}{Z_{2}\left( {1 - {\omega^{2}{LC}}} \right)} = {{\omega \; {CZ}_{2}} = {\tan \left( \frac{\pi}{4} \right)}}} & (6)\end{matrix}$

Accordingly, if the phase shifter 124 a has a phase difference of π/4,the inductance of the inductor L1 a is given by L=Z₂/2ω and thecapacitance of the capacitor C3 a is given by C=1/ωZ₂. At this time, asgiven in equation (7) below, the impedance Z₁ (i.e., the impedancecorresponding to the impedance Z_(Q) illustrated in FIG. 6) becomes areal number.

$\begin{matrix}{Z_{1} = {\frac{{\left( {1 - {\omega^{2}{LC}}} \right)Z_{2}} + {j\; \omega \; L}}{{j\; \omega \; {CZ}_{2}} + 1} = \frac{Z_{2}}{2}}} & (7)\end{matrix}$

As described above, the power amplifier module 100 may be designed suchthat the impedance Z_(Q) becomes a real number while ensuring isolationbetween the amplifiers in the unbalanced mode. That is, the poweramplifier module 100 allows the transistors to operate at higherperformance than the transistors in the comparative example 10, and canimprove the linearity of the transistors.

While the power amplifier module 100 has a configuration in which theresistance element R2 and the capacitor C2 are disposed close to thecombining circuit 120, the resistance element R2 and the capacitor C2may be disposed close to the divider circuit 110. The order in which theresistance element R2 and the capacitor C2 are arranged is not limitedto that illustrated in the drawings, and the resistance element R2 maybe arranged closer to the combining circuit 120 than the capacitor C2.

While FIG. 1 illustrates a configuration including single-stageamplifiers, the number of stages of amplifiers is not limited to one.Two or more stages of amplifiers may be used. In a power amplifiermodule including two or more stages of amplifiers, amplifiers in thefinal stage (power stage) exhibit maximum output power compared withamplifiers in the other stages. Thus, it is desirable that theamplifiers in the final stage have the illustrated configuration.

In the power amplifier module 100, two amplification paths are used, byway of example but not limitation. The number of amplification paths isnot limited to this, and three or more amplification paths may be used.

FIG. 9 is a diagram illustrating another example configuration of thepower amplifier module according to the first embodiment of the presentdisclosure. The same or substantially the same components as those inthe power amplifier module 100 illustrated in FIG. 1 are assigned thesame numerals and are not described herein. Features common to the firstembodiment and this and subsequent embodiments are not described andonly the differences from the first embodiment will be described. Inparticular, similar effects achieved using similar configurations willnot be repeatedly described in the individual embodiments. A poweramplifier module 100A further includes an inductor L2, a capacitor C4,and an output matching network (MN) 130 in addition to the configurationof the power amplifier module 100.

The inductor L2 and the capacitor C4 form a bias circuit that suppliesvoltage or current to the collectors of the transistor Q1 a and thetransistor Q1 b. Specifically, the inductor L2 has an end to which apower supply voltage Vcc is supplied and another end electricallyconnected to an output terminal of the combining circuit 120. Theinductor L2 prevents or reduces a cross talk of the RF signal from thesignal line to a power supply. The capacitor C4 has an end to which thepower supply voltage Vcc is supplied and another end grounded. Thecapacitor C4 is a decoupling capacitor that stabilizes the power supplyvoltage Vcc.

The output matching network 130 has an end to which the amplified signalRFout1 is supplied and another end from which an output signal RFout2 isoutput. The output matching network 130 is a circuit that performsimpedance matching between the combining circuit 120 in the precedingstage and a load (for example, 50Ω) in the subsequent stage. The outputmatching network 130 is constituted by, for example, a capacitor and aninductor.

With the configuration described above, the power amplifier module 100Acan also achieve advantages similar to those of the power amplifiermodule 100. In the power amplifier module 100A, in addition, a singlebias circuit can supply voltage or current to both the collector of thetransistor Q1 a and the collector of the transistor Q1 b. Thus, thisconfiguration can reduce the circuit scale compared with a configurationin which respective bias circuits are used to supply voltage or currentto the collectors of the transistors.

FIG. 10 is a diagram illustrating another example configuration of thepower amplifier module according to the first embodiment of the presentdisclosure. The same or substantially the same components as those inthe power amplifier module 100A illustrated in FIG. 9 are assigned thesame numerals and are not described herein. A power amplifier module100B further includes harmonic termination circuits 140 a and 140 b inaddition to the configuration of the power amplifier module 100A.

The harmonic termination circuit 140 a (first harmonic terminationcircuit) is connected to the collector (output terminal) of thetransistor Q1 a, and short-circuits a harmonic (such as the second orthird harmonic) of the amplified signal output from the transistor Q1 a.Likewise, the harmonic termination circuit 140 b (second harmonictermination circuit) is connected to the collector (output terminal) ofthe transistor Q1 b, and short-circuits a harmonic (such as the secondor third harmonic) of the amplified signal output from the transistor Q1b. The configuration of the harmonic termination circuits 140 a and 140b is not limited to any specific type. For example, each of the harmonictermination circuits 140 a and 140 b may be an LC series resonantcircuit having a resonant frequency equal to a harmonic frequency of thecorresponding amplified signal.

With the configuration described above, the power amplifier module 100Bcan also achieve advantages similar to those of the power amplifiermodule 100. In addition, since the harmonic termination circuits 140 aand 140 b attenuate harmonics, the power amplifier module 100B canexhibit improved power efficiency compared with the power amplifiermodules 100 and 100A.

FIG. 11 is a diagram illustrating an example configuration of a poweramplifier module according to a second embodiment of the presentdisclosure. The same or substantially the same components as those inthe power amplifier module 100 illustrated in FIG. 1 are assigned thesame numerals and are not described herein. Unlike the configuration ofthe power amplifier module 100, a power amplifier module 200 includes acombining circuit 210 instead of the combining circuit 120, and aninductor L3 instead of the capacitor C2.

The combining circuit 210 includes a capacitor C5 a (third capacitor), acapacitor C5 b (fourth capacitor), an inductor L4 (fourth inductor), andthe combiner 122. The capacitor C5 a is connected in series between thecollector of the transistor Q1 a and the combiner 122, and the capacitorC5 b is connected in series between the collector of the transistor Q1 band the combiner 122. The inductor L4 has an end connected to thecombiner 122 and another end grounded. The inductor L4 has an inductancethat is approximately half the inductance of the inductor L3, forexample.

The inductor L3 (third inductor) is connected in parallel to theresistance element R2. Specifically, the inductor L3 has an endconnected to the collector of the transistor Q1 a and another endconnected to the collector of the transistor Q1 b.

The power amplifier module 200 has a configuration such that some of thecapacitors in the power amplifier module 100 are replaced by inductorsand the inductors in the power amplifier module 100 are replaced bycapacitors. That is, the combining circuit 210 in the power amplifiermodule 200 includes a phase shifter (third phase shifter) constituted bythe capacitor C5 a connected in series with the signal path and theinductor L4 shunt-connected to the signal path, and a phase shifter(fourth phase shifter) constituted by the capacitor C5 b connected inseries with the signal path and the inductor L4 shunt-connected to thesignal path. Each of the phase shifters has a configuration similar tothat of an L-type high pass filter (HPF), and the constants of therespective elements in the phase shifters are designed such that thephase of an output signal is advanced by about 45 degrees with respectto the phase of an input signal.

Also in the combining circuit 210, as in the combining circuit 120illustrated in FIG. 1, in the unbalanced mode, the phase of the signalfrom the output terminal of the transistor Q1 a to the output terminalof the transistor Q1 b through the capacitor C5 a, the inductor L4, andthe capacitor C5 b is advanced by about 90 degrees, and the phase of thesignal from the output terminal of the transistor Q1 a to the outputterminal of the transistor Q1 b through the inductor L3 is delayed byabout 90 degrees. Thus, isolation is ensured between the amplifiers inthe unbalanced mode. In the balanced mode, the impedance Z_(Q) on theload side as seen from the output of the amplifiers can become a realnumber. Therefore, the power amplifier module 200 can achieve advantagessimilar to those of the power amplifier module 100.

FIG. 12 is a diagram illustrating another example configuration of thepower amplifier module according to the second embodiment of the presentdisclosure. The same or substantially the same components as those inthe power amplifier module 200 illustrated in FIG. 11 are assigned thesame numerals and are not described herein. A power amplifier module200A further includes inductors L5 a and L5 b, capacitors C6 a and C6 b,and the output matching network 130 in addition to the configuration ofthe power amplifier module 200.

The inductor L5 a and the capacitor C6 a form a bias circuit thatsupplies voltage or current to the collector of the transistor Q1 a, andthe inductor L5 b and the capacitor C6 b form a bias circuit thatsupplies voltage or current to the transistor Q1 b. Specifically, theinductor L5 a has an end to which a power supply voltage Vcc is suppliedand another end electrically connected to a node of the collector of thetransistor Q1 a and the capacitor C5 a. The inductor L5 b has an end towhich the power supply voltage Vcc is supplied and another endelectrically connected to a node of the collector of the transistor Q1 band the capacitor C5 b. Each of the capacitors C6 a and C6 b has an endto which the power supply voltage Vcc is supplied and another endgrounded. The functions of the inductors L5 a and L5 b and thecapacitors C6 a and C6 b are similar to those of the inductor L2 and thecapacitor C4 in the power amplifier module 100A and are not described indetail herein.

The output matching network 130 has an end to which the amplified signalRFout1 is supplied and another end from which an output signal RFout2 isoutput.

With the configuration described above, the power amplifier module 200Acan also achieve advantages similar to those of the power amplifiermodule 100. In the power amplifier module 200A, in addition, biascircuits that supply voltage or current to the collectors are connectedin parallel. With this configuration, the parasitic resistance of theinductors L5 a and L5 b and the capacitors C6 a and C6 b isapproximately half that in a configuration in which bias circuits thatsupply voltage or current to the collectors are not connected inparallel. As a result, an improvement in performance such as linearityof an output signal can be achieved.

Like the power amplifier module 100B illustrated in FIG. 10, the poweramplifier modules 200 and 200A may include the harmonic terminationcircuits 140 a and 140 b.

FIG. 13 is a diagram illustrating an example of the mounting of thepower amplifier module according to the first embodiment of the presentdisclosure. The constituent elements of the power amplifier module aresimilar to those of the power amplifier module 100A illustrated in FIG.9 and are not described herein.

As illustrated in FIG. 13, in the power amplifier module 100A, thedivider circuit 110, the transistors Q1 a and Q1 b, the resistanceelements R1 a, R1 b, and R2, and the capacitors C2 and C3 are integratedon the same substrate, namely, on a substrate 150. The substrate 150 maybe, for example, a monolithic microwave integrated circuit (MMIC). Thisconfiguration can reduce the circuit scale. The inductors L1 a and L1 bmay be mounted on a module in which the power amplifier module 100A isformed, by using surface mount device (SMD), wiring, or any othertechnique.

On the substrate 150, the resistance element R2 and the capacitors C2and C3 may be mounted between the transistor Q1 a and the transistor Q1b. On the substrate 150, furthermore, when the principal surface of thesubstrate 150 is viewed in plan, a set of paired elements (such as thetransistor Q1 a and the transistor Q1 b or the capacitor C1 a and thecapacitor C1 b) may be arranged substantially symmetrically with respectto a line in such a manner as to be centered around a set of unpairedelements (such as the resistance element R2 and the capacitors C2 andC3). A set of paired elements are arranged substantially symmetricallywith respect to a line, which can prevent or reduce imbalance in signalbetween the two amplification paths.

In a power amplifier module including the harmonic termination circuits140 a and 140 b illustrated in FIG. 10, the harmonic terminationcircuits 140 a and 140 b may also be mounted substantially symmetricallywith respect to a line on the substrate 150. This also applies to anexample of the mounting of the power amplifier module according to thesecond embodiment described below.

FIG. 14 is a diagram illustrating an example of the mounting of thepower amplifier module according to the second embodiment of the presentdisclosure. The constituent elements of the power amplifier module aresimilar to those of the power amplifier module 200A illustrated in FIG.12 and are not described herein.

As illustrated in FIG. 14, in the power amplifier module 200A, thedivider circuit 110, the transistors Q1 a and Q1 b, the resistanceelements R1 a, R1 b, and R2, the inductor L3, and the capacitors C5 aand C5 b are integrated on the same substrate, namely, on a substrate152. The substrate 152 may be an MMIC, for example. This configurationcan reduce the circuit scale. The inductor L4 may be mounted on a modulein which the power amplifier module 200A is formed, by using SMD,wiring, or any other technique.

On the substrate 152, the resistance element R2 and the inductor L3 maybe mounted between the transistor Q1 a and the transistor Q1 b. On thesubstrate 152, furthermore, when the principal surface of the substrate152 is viewed in plan, a set of paired elements (such as the transistorQ1 a and the transistor Q1 b or the capacitor C1 a and the capacitor C1b) may be arranged substantially symmetrically with respect to a line insuch a manner as to be centered around a set of unpaired elements (suchas the resistance element R2 and the inductor L3).

Exemplary embodiments of the present disclosure have been described. Thepower amplifier modules 100, 100A, and 100B include the capacitor C2that electrically connects the collectors of the transistors Q1 a and Q1b to each other, and the combining circuit 120 includes the inductors L1a and L1 b, which are connected in series with a signal path, and thecapacitor C3, which is shunt-connected to the signal path. With thisconfiguration, the phase of an amplified signal output from thecollector of the transistor Q1 a is delayed by about 45 degrees bypassing through the phase shifter 124 a including the inductor L1 a andthe capacitor C3, and is delayed by about 45 degrees by passing throughthe phase shifter 124 b including the inductor L1 b and the capacitorC3. Further, the phase of the amplified signal output from the collectorof the transistor Q1 a is advanced by about 90 degrees by passingthrough the capacitor C2. Accordingly, even if an amplified signal inone amplification path enters the other amplification path, the signalhas amplitudes that cancel each other out, and isolation is ensuredbetween the amplifiers. In addition, the configuration can be designedsuch that the impedance Z_(Q) on the combining circuit side as seen fromthe transistors Q1 a and Q1 b becomes a real number, which can improvethe linearity of the transistors compared with the comparative example.

In the power amplifier modules 100, 100A, and 100B, furthermore, thecapacitor C3 may have a capacitance that is about twice the capacitanceof the capacitor C2.

In the power amplifier modules 100, 100A, and 100B, furthermore, thedivider circuit 110, the transistors Q1 a and Q1 b, the resistanceelement R2, and the capacitors C2 and C3 may be formed on the samesubstrate. This configuration can reduce the circuit scale.

Further, the power amplifier modules 200 and 200A include the inductorL3 that electrically connects the collectors of the transistors Q1 a andQ1 b to each other, and the combining circuit 210 includes thecapacitors C5 a and C5 b, which are connected in series with a signalpath, and the inductor L4, which is shunt-connected to the signal path.With this configuration, the phase of an amplified signal output fromthe collector of the transistor Q1 a is advanced by about 45 degrees bypassing through a phase shifter including the capacitor C5 a and theinductor L4, and is advanced by about 45 degrees by passing through aphase shifter including the capacitor C5 b and the inductor L4. Inaddition, the phase of the amplified signal output from the collector ofthe transistor Q1 a is delayed by about 90 degrees by passing throughthe inductor L3. Accordingly, even if an amplified signal in oneamplification path enters the other amplification path, the signal hasamplitudes that cancel each other out, and isolation is ensured betweenthe amplifiers. In addition, the configuration can be designed such thatthe impedance Z_(Q) on the combining circuit side as seen from thetransistors Q1 a and Q1 b becomes a real number, which can improve thelinearity of the transistors compared with the comparative example.

In the power amplifier modules 200 and 200A, furthermore, the inductorL4 may have an inductance that is approximately half the inductance ofthe inductor L3.

In the power amplifier module 200, furthermore, the divider circuit 110,the transistors Q1 a and Q1 b, the resistance element R2, the inductorL3, and the capacitors C5 a and C5 b may be formed on the samesubstrate. This configuration can reduce the circuit scale.

Further, the power amplifier module 100B includes the harmonictermination circuits 140 a and 140 b connected to the collectors of thetransistors Q1 a and Q1 b, respectively. This configuration attenuatesharmonics from the amplified signals obtained by the transistors Q1 aand Q1 b. Thus, the power amplifier module 100B can exhibit improvedpower efficiency compared with the power amplifier modules 100 and 100A.

The embodiments described above are intended to help easily understandthe present disclosure, and are not to be used to construe the presentdisclosure in a limiting fashion. Various modifications or improvementscan be made to the present disclosure without departing from the gist ofthe present disclosure, and equivalents thereof are also included in thepresent disclosure. That is, the embodiments may be appropriatelymodified in design by those skilled in the art, and such modificationsalso fall within the scope of the present disclosure so long as themodifications include the features of the present disclosure. Forexample, the elements included in the embodiments described above andthe arrangement, materials, conditions, shapes, sizes, and the likethereof are not limited to those described in the illustrated examplesbut can be modified as appropriate. Furthermore, the embodiments areillustrative. It is to be understood that elements included in differentembodiments can be partially replaced or combined with each other andsuch replacements or combinations of elements also fall within the scopeof the present disclosure so long as the replacements or combinations ofelements include the features of the present disclosure.

While preferred embodiments of the disclosure have been described above,it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the disclosure. The scope of the disclosure, therefore, isto be determined solely by the following claims.

What is claimed is:
 1. A power amplifier module comprising: a dividercircuit that divides an input signal into a first signal and a secondsignal; a first amplifier that amplifies the first signal and outputs athird signal; a second amplifier that amplifies the second signal andoutputs a fourth signal; a combining circuit that combines the thirdsignal and the fourth signal and that outputs an amplified signal of theinput signal; a resistance element that electrically connects an outputterminal of the first amplifier and an output terminal of the secondamplifier to each other; and a first capacitor connected in parallel tothe resistance element, wherein the combining circuit comprises: acombiner, a first inductor connected in series between the outputterminal of the first amplifier and the combiner, a second inductorconnected in series between the output terminal of the second amplifierand the combiner, and a second capacitor having a first end connected tothe combiner and a second end grounded, the first inductor and thesecond capacitor together forming a first phase shifter and the secondinductor and the second capacitor together forming a second phaseshifter, wherein a phase of the third signal from the output terminal ofthe first amplifier to the output terminal of the second amplifierthrough the combiner is delayed by about 45 degrees in the first phaseshifter, and is delayed by about 45 degrees in the second phase shifter,and wherein a phase of the third signal from the output terminal of thefirst amplifier to the output terminal of the second amplifier throughthe first capacitor is advanced by about 90 degrees.
 2. The poweramplifier module according to claim 1, wherein a capacitance value ofthe second capacitor is about twice a capacitance value of the firstcapacitor.
 3. The power amplifier module according to claim 1, whereinthe divider circuit, the first amplifier, the second amplifier, theresistance element, the first capacitor, and the second capacitor areformed on a single substrate.
 4. The power amplifier module according toclaim 2, wherein the divider circuit, the first amplifier, the secondamplifier, the resistance element, the first capacitor, and the secondcapacitor are formed on a single substrate.
 5. The power amplifiermodule according to claim 1, further comprising: a first harmonictermination circuit connected to the output terminal of the firstamplifier, the first harmonic termination circuit short-circuiting aharmonic of the third signal; and a second harmonic termination circuitconnected to the output terminal of the second amplifier, the secondharmonic termination circuit short-circuiting a harmonic of the fourthsignal.
 6. The power amplifier module according to claim 2, furthercomprising: a first harmonic termination circuit connected to the outputterminal of the first amplifier, the first harmonic termination circuitshort-circuiting a harmonic of the third signal; and a second harmonictermination circuit connected to the output terminal of the secondamplifier, the second harmonic termination circuit short-circuiting aharmonic of the fourth signal.
 7. The power amplifier module accordingto claim 3, further comprising: a first harmonic termination circuitconnected to the output terminal of the first amplifier, the firstharmonic termination circuit short-circuiting a harmonic of the thirdsignal; and a second harmonic termination circuit connected to theoutput terminal of the second amplifier, the second harmonic terminationcircuit short-circuiting a harmonic of the fourth signal.
 8. The poweramplifier module according to claim 4, further comprising: a firstharmonic termination circuit connected to the output terminal of thefirst amplifier, the first harmonic termination circuit short-circuitinga harmonic of the third signal; and a second harmonic terminationcircuit connected to the output terminal of the second amplifier, thesecond harmonic termination circuit short-circuiting a harmonic of thefourth signal.
 9. A power amplifier module comprising: a divider circuitthat divides an input signal into a first signal and a second signal; afirst amplifier that amplifies the first signal and outputs a thirdsignal; a second amplifier that amplifies the second signal and outputsa fourth signal; a combining circuit that combines the third signal andthe fourth signal and that outputs an amplified signal of the inputsignal; a resistance element that electrically connects an outputterminal of the first amplifier and an output terminal of the secondamplifier to each other; and a third inductor connected in parallel tothe resistance element, wherein the combining circuit comprises: acombiner, a third capacitor connected in series between the outputterminal of the first amplifier and the combiner, a fourth capacitorconnected in series between the output terminal of the second amplifierand the combiner, and a fourth inductor having a first end connected tothe combiner and a second end grounded, the third capacitor and thefourth inductor together forming a third phase shifter and the fourthcapacitor and the fourth inductor together forming a fourth phaseshifter, wherein a phase of the third signal from the output terminal ofthe first amplifier to the output terminal of the second amplifierthrough the combiner is advanced by about 45 degrees in the third phaseshifter, and is advanced by about 45 degrees in the fourth phaseshifter, and wherein a phase of the third signal from the outputterminal of the first amplifier to the output terminal of the secondamplifier through the third inductor is delayed by about 90 degrees. 10.The power amplifier module according to claim 9, wherein an inductancevalue of the fourth inductor is approximately half an inductance valueof the third inductor.
 11. The power amplifier module according to claim9, wherein the divider circuit, the first amplifier, the secondamplifier, the resistance element, the third inductor, the thirdcapacitor, and the fourth capacitor are formed on a single substrate.12. The power amplifier module according to claim 10, wherein thedivider circuit, the first amplifier, the second amplifier, theresistance element, the third inductor, the third capacitor, and thefourth capacitor are formed on a single substrate.
 13. The poweramplifier module according to any one of claim 9, further comprising: afirst harmonic termination circuit connected to the output terminal ofthe first amplifier, the first harmonic termination circuitshort-circuiting a harmonic of the third signal; and a second harmonictermination circuit connected to the output terminal of the secondamplifier, the second harmonic termination circuit short-circuiting aharmonic of the fourth signal.
 14. The power amplifier module accordingto any one of claim 10, further comprising: a first harmonic terminationcircuit connected to the output terminal of the first amplifier, thefirst harmonic termination circuit short-circuiting a harmonic of thethird signal; and a second harmonic termination circuit connected to theoutput terminal of the second amplifier, the second harmonic terminationcircuit short-circuiting a harmonic of the fourth signal.
 15. The poweramplifier module according to any one of claim 11, further comprising: afirst harmonic termination circuit connected to the output terminal ofthe first amplifier, the first harmonic termination circuitshort-circuiting a harmonic of the third signal; and a second harmonictermination circuit connected to the output terminal of the secondamplifier, the second harmonic termination circuit short-circuiting aharmonic of the fourth signal.
 16. The power amplifier module accordingto any one of claim 12, further comprising: a first harmonic terminationcircuit connected to the output terminal of the first amplifier, thefirst harmonic termination circuit short-circuiting a harmonic of thethird signal; and a second harmonic termination circuit connected to theoutput terminal of the second amplifier, the second harmonic terminationcircuit short-circuiting a harmonic of the fourth signal.